Dark matter halos were identified with spherical-overdensity halo finders Bound Density Maximum (BDM) and/or Robust Overdensity Calculation using K-Space Topologically Adaptive Refinement (RockStar). Short description of the halo finders is here. BDM is described in Appedix A of Riebe et al. (2011) and for convenience is reproduced here.

RockStar and BDM halo finders were extensively studied and compared: see here and here. Both BDM and RockStar identify distinct halo and sub halos, but they use different algorithms to do it. The main difference between BDM in RockStar is in masses of sub halos with RockStar giving bigger masses. Circular velocities show much smaller differences.

Halo identification for GLAM simulations is done with a strip-down version of BDM halo finder. In this case only distinct halos are identified and listed in catalogs.

There are two types of BDM catalogs that differ by the definition of the viral radius. Catalogs with filenames having capital letter V (e.g., CatshortV.0416.DAT) are for the verdensity 360*ρback (background density). Catalogs with capital letter W are for 200*ρcrit (critical density) for defining the halo boundary.